The present invention relates to a truck for a railway vehicle and, more particularly, to a truck which is suitable for a railway vehicle running on a curved track at a high speed.
As shown in FIGS. 1, 2, 3 and 4, a conventional railway vehicle with a truck using rolling rubber springs for a journal box support device includes a car body 1, an air spring 2, and a truck frame 3, with the car body 1 being supported on the truck frame 3 by the air springs 2. A journal box locating means 4 locates and fits a journal box 5 to the truck frame 3, with the journal boxes 5 being disposed at both ends of a wheel-and-axle 6. The journal box locating means 4 locates the wheel-and-axle 6 to the truck frame 3 via the journal box 5, and buffers the relative displacement of the wheel-and-axle 6 to the truck frame 3 in the vertical direction. The journal box locating means 4 also restricts the movement of the wheel-and-axle 6 in both longitudinal and transverse directions within a horizontal plane relative to the truck frame 3.
As shown in FIGS. 3 and 4, the journal box locating means 4 includes a center core 11, a rubber ring 10 and an outer housing 9. The center cores 11 are disposed and fitted by nuts 7 to the journal box 5 in the longitudinal direction of the car body. The center core 11 is inserted into the rubber ring 10, and supports the outer housing 9 through the rubber ring 10. The outer housing 9 is fitted to the lower-surface of the truck frame 3 at the fitting position of the journal box. An axle box hanger is vertically disposed on the center of the journal box 5 and a hole is bored on the truck frame 3 so that the axle box hanger can be inserted therein. The axle box hanger is fitted to the truck frame 3 by a set metal 8 while it is kept inserted into the hole of the truck frame 3. The set metal 8 penetrates through an elongated hole disposed on the axle box hanger so that the latter can move vertically.
The journal box locating means 4 operates and functions in the following manner. The rubber ring 10 is interposed between the outer housing 9 and the center core 11. While being pushed by the relative displacement between the outer housing 9 and the center core 11 in the vertical direction and rolling, the rubber ring 10 exhibits the spring or buffering action. The deformation of the rubber ring 10 buffers the relative displacement between the outer housing 9 and the center core 11 in the longitudinal direction within a horizontal plane. According to the construction described above, however, the center line of each of the outer housing 9 and the center core 11 is disposed vertically in order to accurately locate the wheel-and axle 6 to the truck frame 3. This construction is light in weight and simple as a journal box support structure. When the truck runs on a curved track, however, the steering function of the wheel-and-axle 6 is nothing but tread force steering effected by the padient of the wheel tread, and the steering quantity brought forth by this tread force steering is not sufficient. Particularly when the truck runs on the curved track at a high speed, the flange wear of the wheel and the wear of the rail increase.
In order to eliminate the problem described above, a steering truck has been developed which has a construction such that the truck is caused to rock in such a direction so as to bring the center line of the wheel-and-axle 6 of the truck into agreement with the center of radius of curvature of a curved track when the truck runs on the curved track. For example, in Japanese Patent Publication No. 11538/1980 (corresponding to U.S. Pat. No. 3,948,188) a truck is proposed wherein the portions of the truck frame corresponding to the side frames consist of swing arms. When the truck runs on a curved track, the load-bearing capacities change at both side positions of the truck. That is, a large load acts on the outer rail side of the truck and the load drops on the inner rail side. This change of load-bearing capacities causes the swing arms to rock, and the angle of inclination of the swing arm changes. Thus, the wheel base of the truck is extended or contracted due to the rock of the swing arm, thereby effecting the steering operation.
In accordance with this construction, however, the axle spring must be composed of a laminated spring, but this laminated spring might impede comfortability design. When a driving bogie equipped with a motor is to be produced, it becomes difficult to support the motor because the construction of the truck frame is not a rigid frame bogie, and hence the construction might become complicated.
Another steering truck is described in Japanese patent Publication No. 20562/1973 and Japanese Utility Model Publication No. 24097/1973 wherein the journal box is mounted to the truck frame by supporting leaf springs or links, with the supporting leaf springs or links being fitted in such a fashion that they are inclined when the truck runs on an ordinary linear track. The angle of inclination of the supporting leaf springs or links is changed by the change of load-bearing capacities at the right and left positions of the truck when it runs on a curved track. The change of the angle of inclination in turn extends or contracts the wheel base, thereby effecting the steering operation of the wheel-and-axle. Since the truck frame of this truck is a rigid truck frame, no problem occurs, in particular, when a motor or the like is mounted to the truck to obtain a driving bogie. However, the journal box of this prior art truck must be located and fitted to the truck frame using the supporting leaf springs or links. Therefore, the number of necessary components and weight increase, and the cost of production is proportionately increased. In addition, inspection and maintenance becomes also more troublesome. In accordance with this construction, the journal box is moved within a horizontal plane by the elastic deformation of the supporting leaf springs resulting from the relative displacement between the journal box and the truck frame in the vertical direction, or by the rock of the links. The movement of the journal box within the horizontal plane causes the steering operation of the wheel-and-axle. In the steering operation of the wheel-and-axle described above, the supporting leaf springs or links rotate with a certain point being the center, and hence the orbit of relative movement of the journal box to the truck frame describes an arc. In order to obtain the optimal steering operation of the wheel-and-axle, however, the orbit of relative movement of the journal box to the truck frame must be linear so that steering is proportional to the change of the load-bearing capacities at the right and left positions of the truck frame. If the journal box is mounted to the truck frame by the supporting leaf springs or links as in the prior art truck, the orbit of relative movement of the journal box to the truck frame becomes an arc as described above, and the optimum steering operation can not be accomplished. Though this disadvantage might be solved by increasing the radius of rotation of the supporting leaf springs or links, this makes it difficult, in turn, to reduce the size or weight of the truck.